Flat low melting point metal filament having an oriented synthetic resin sheath



Sept. 26, 1961 3,001,265 MEN'I' HAVING SHEATH R. W. BUN FLAT LOW MELTING POINT METAL FILA AN ORIENTED SYNTHETIC RESIN 1957 3 Sheets-Sheet 1 Filed March 25,

Iii 20 ATTORNEY Sept. 26, 1961 R. w. BUNDY 3,001,265

FLAT LOW MELTING POINT METAL FILAMENT HAVING 7 AN ORIENTED SYNTHETIC RESIN SHEATH Filed March 25, 1957 5 Sheets$heet 2 FIG. 8

INVENTOR ROBERT W. BUNDY I ATTORNEY 3,001,265 SAVING Sept. 26, 1961 R. w. BUNDY FLAT LOW MELTING POINT METAL FILAMENT AN ORIENTED SYNTHETIC RESIN SHEAT Filed March 25, 1957 3 Sheets-Sheet 3 FIG. I?)

FIG. l6

FIG.|5

m m M R E W 0 Mm W. n m

E w 1 R 0 Patented Sept. 26, 1961 6 Claims. (Cl/ZS-SZ) This invention isrelated to fiat-filaments and ribbons of polymeric material having a metal core and to a process and apparatus for producing same. It is particularly 7 concerned with decorative ribbons and special insulated conductors comprising a metal core embedded in a synthetic linear polymer.

The use of .polymers as electrical insulators is well known. Such polymers have been applied to preformed wires from a solution of the polymer, from a dispersion of the polymer followed by coalescence or fusion and from a melt of the polymer. All such processes have had disadvantages-of nonuniform coating, limited thickness, and the presence of hazardous conditions when using solutions of polymers such as polyamides and polyesters. I

A serious limitation on the previous methods ofcoating electrical conductors is the fact that in the case of very fine wires, their handling during the coatingoperation as well as the proper application of the coating are quite ditlicult. Many types of conductors that would be of great utility if coated, do not lend themselves to conventional coating processes because of their inherent weakness'when in the form of very small diameter wires. Furthermore, in order to obtain very fine wires, long and expensive wire drawing and annealing steps are required, thereby adding considerab-ly'to the cost of the final insulated' product. V 1 v i It is known to eject a mixture ofa molten metal and a fiber-forming polymer into an air jet to produce short curled filaments with irregularand non-uniform structure but such process does not relate to the making of continuous filaments having a predetermined and definite core and sheath.

The most desirable physical properties of polymers such as polyamides and polyesters are obtained-through orientation of the polymers by a drawingoperation which usually extends the polymer to two or more times'its original length, depending on the degree of orientation and the filament denier desired. The usual coating procedure produces little, if any, orientation. "Itis possible tofpartially orient the coating by drawing a metal core coated with a molten polymer througha die at a rate such 'that the core moves faster than .thecoatingl This method -thatmelts at or below thetemperature at which the polypolymer.

metal in such a product is much lower than that of the polymer, so that the strength of filaments made by this process is less than that desired for many purposes.

It has been proposed to make decorative ribbon by laminating a thin metal film between two plastic films and then slitting the laminate to strips. By its very nature, such a process is very time consuming and expensive and is applicable to the production of only relatively large denier ribbons. Also, such products have been limited, from a practical standpoint, to those having continuous metal inserts.

It is an objectof this invention to produce a continuous relatively fiat filament of relatively small denier, particularly the deniers used in textiles, comprising a continuous metal core surrounded by a highly oriented synthetic polymer sheath. A further object is the production of decorative continuous filaments with a ribbon-like crosssection comprising a reflective continuous metal core enclosed in a sheath of an oriented synthetic polymer. A

further object is the production of continuous filaments containing a longitudinal row of flat reflective platelets of a metal completely covered by an oriented synthetic Other objects will appear hereinafter. The objects of this invention have-been attained by simultaneously spinning a molten polymer and a metal '1116101' its solution is extruded, as a continuous sheath and core respectively of a composite filament, and then submitting the filament to rolling and/or drawing in such sequence as is desired to produce a flattened cross-section both forthe sheath and core with the desired eifects referred to herein.

Apparatus shown in the application of Alvin L. Breen filed of even date herewith and entitled MetalCore Composite Filaments'is admirably suited for the production ent inventionincludes also a special apparatus particular- 1y adapted for the making of single multi-compo'nent filaproduces, however, only a negligible amount of orientation since the percent of draw is limited to the amount of draw given to the'metal and is generally not in excess of 10% draw, the percent of draw being the percent of the original length that is permanently added (i.e'., not regained by release of the drawing tension) during the drawing operation. I

As a'result 'oftheir limitations, the coated conductors I of the prior art have depended upon the metal core itself metal core. In general, the limit of elongation "o f the of FIGURE 3;

ments and theinvention will be particularly described with respect to this novel apparatus I Referring to the drawings, s FIGURE 1 is an end view of the spinning block forming part of a spinneret assembly suitable for making fila- -ments of this invention;

-FIGURE 2 is an elevation in section, along plane 2- 2 of-F'IGURE "l, of the spinning block of FIGURE 1;

FIGURE 2A is a detailed view (on a larger scale) of a screw-threaded hole shown in FIGURE 2;

FIGURE 3 is an end view of the bottom or spinning plate containing the spinning orifice and adapted to be attached to the spinning block of FIGURES l and 2;

FIGURE-4 is an elevation in section along plane 4-44 FIGURE 4A is a detailed view (magnified) of the spinhing-orifice and chamber communicating therewith'for the reception of a plug adapted to permit the conducting of spinning fluid to the spinning orifice;

FIGURE 5 is an elevation of avdesign of plu'g 'to'b'e received into the spinningplate of FIGURE 4for the conducting of spinning fluid to the spinning orifice; I

FIGURE 6 is an end view of the plug of FIGURE f5 showing the peripheral shape of the plug; I r FIGURE? is a front elevation in section along 'a central plane showing the spinning block and spinning plate,

together with the fluid conducting plug, .in assembled position. e

The equipment shown in the figures is adapted to be used in verticalposition as shown in FIGURE 7fbut FIGURES 1- 6 inclusive are shown inhorizontalpositidn for ease of illustration.

FIGURES 8-1 6 inclusive are schematierepres'entations p or filaments in lengthwise and cross-sectional view made in accordance with the invention. In all instancespolymeric sheath 100 surrounds metal core material 101.

,Referring to the drawings, spinning block 1 having enlarged portion 2 providedwith a shoulder 3 (for holding the spinning assembly in a suitable, support) is shaped with a chamber 4, for receiving molten polymer and also for the reception of suitable filtering means (not shown) forthe polymer. Spinning block 1 is provided with eccen trically disposed canal 5 for leading the molten polymer downwardly to the spinning plate.

. "Spinning block 1 is also provided with a passage 6 provided with a screw-threaded portion (as shown) Y adapted to receive the screw-threaded end of a conduit for leading molten metal into thespinning block. Hole 6 leads into passage 7 which terminates in a counterbore 8 larger in diameter than passage 7. Counterbore 8 leads into screwthreaded hole 9, the end of which is machined fiat and parallel with the bottom surface of spinning block 1. Spinning block 1 is provided with several screw-threaded holes 10 for the reception of securing bolts as will be discussed in more detail hereinafter.

Bottom or spinning plate 11 is a fiat circular plate of the same diameter as the bottom of spinning block 1 and is adapted to be secured to spinning block 1 by means of bolts 12 to, be inserted through holes 13in spinning plate 11 having enlarged heads received in counterbore 14 in spinning plate 11. The spinning plate is provided with a circular, shallow chamber" 15 into which the polymer channel 5 opens for the leading of the molten polymer into chamber 15. Spinning plate 11 is formed at its center with circular bore 16 connecting with spinneret orifice 17. a

The plug-shaped'member 18 has an enlarged end 19 formed with four flat sides 20 forming chords of a circle of the same diameter as chamber 16 in the spinning plate with the chordsterminating inarcuate portions 21 form-' tion with the bottom oflplu'g'end 19 clear" of the bottom 1 of hole16 to permit passage of fluid around plug 18 to the spinning orifice. Plug 18 is bored throughout the l greater part of its length with channel 24 of the same diameter as conduit 7 for the leading of molten metal to the spinning orifice. Conduit 24 (shown in dotted lines .in FIGURE 5) tapers (as shown) to a small diameter hole 25 of capillary size which extends through small dining of single filaments, as distinct from the number of filaments normally spun for the making of yarn. It will be understood, however, that the invention is not limited to the use of a single-hole spinneret, but can be applied as stated above, to the simultaneous extrusion of a number of filaments, e.g., by the use of the spinneret of the aforesaid Breen patent application filed of even date herewith.

If desired, gaskets can be inserted between the spirining plate and the spinning block so as to insure that no,

leakage of spinning material will take place. Screwthreaded bolts 14 insure accurate and tight'assembly of the parts of the equipment for the production of filaments of the desired uniform sheath-core form.

The apparatusdepicted is connected with suitable pipingand filtration apparatus as maybe required'to supply a molten polymer and a molten metal and is kept at'a temperature sufiiciently high during operation to maintain the polymer and the metal in the molten state.

In the examples, the relative viscosity (1 i. e., theviscosity, of a solution of polymer relative to that of the solameter extension 26 on the outer end of plug 18. Projection 26 is ofsmaller diameter than spinning orifice 17 and is adapted to be receivedin spinning orifice 17 with its end flush with the bottom of spinning plate 11.

, The operation of the above-described apparatus can be readily understood. Molten metal is supplied to the spin- {ning block through hole 6 and proceeds through conduit ",7, passage 24 and capillary25 to the spinning orifice.

Molten polymer from chamber 4 passes throughconduit .5 to pool chamber '15, through the passage between straight, sides 20 of the plug 18 and chamber 16'and is --then extruded through the spinneret orifice 17 as a sheath around the metal core. The sheath-core filament is solidified by contact with a suitable coagulant such as air or water at a temperature considerably below the melting point of the metal and of the polymer.

:The'spinning orifice 17, inclusive of projection 26 of plug 18, is of a diameter within the range of those used ,for spinning textile denier filaments, e.g., 0.010 to 0.10

inch, the size of the spinning orifice being chosen accord- V ing to the size of filament desired.

The aboveequipment is particularly Suitedto the spin- The following examples in which parts, proportions and percentages are by weight unless otherwise specified, are' intended to illustrate this invention and in no manner to 'limit it.

Example 1 Using a l-hole spinneret similar to that shown in FIG- URES 1-7 having an orifice 17 of 0.030 inch diameter surrounding projection 26 of 0.0180 inch outside diameter at the lower face of the spinneret with a passage 25 of 0.008 inch diameter, poly-(ethylene terephthalate) of relative viscosity 37 was melt-spun as a sheath around a molten coreof an alloy comprising 40% bismuth and 60% tin melting; over the range 139-170 (3. The composite filaments werespun at 290" C. and at yards .per minute into a l-foot vertical tube of water at 3390. which' was pumped concurrently with the direction of travel of the extrudedfilament. Good spinning was enjoyed and continuous filaments obtained, a typical cross section of which had a diameter of 0.009 inch and a core 0.006 inch in diameter (equivalent to 45% core by volume); th e filament (magnified) is similar to that shown lengthwise in FIGURE 8 (one filament) and in crosssection in FIGURE 9 (showing several filaments), the metal core, in these figures as elsewhere in the figures of ,the filaments, appearing in black against the sheath shown in light color. The as-spun filamentshad a tensile strength of 9900 pounds per square inch and could only be elongated a maximum of 3.7% without breaking the core at room temperature. A l0-inch length of the as-spun filament conducted a current of 0.67 ampere at 6 volts without fusing or degrading the, polymeric sheath.-

A portion of the as-spun filament was hand-rolled along its length with a metal roller at room temperature into a ribbon approximately 0.050 inch wide and 0.0015 inch; r thick, similar tothat shown in cross-section in FIGURE 10. As shown in FIGURE 10, certain of the filaments were not flattened since the pressure of the hand-roller was not, in this case, effectively applied to all filaments.

rolled product had a tensile strength of 10,400 pounds per square inch.

length (1.7.x

filaments as-spun length (3.5 x).

By changing the relative flow rates of polymer and metal, continuous filaments'containingrespectively 33% and 25% core'by volume wereobtained with an 8-hole spinneret such as that shown in the aforesaid Breen patent application filed of even date herewith, and using the polymer, 1netal and conditions of the above example. Hand drawing of these filaments to1 elongation atroom Example 11 ment was continuously wound up at 121 yards per minute.

The filament (0.0085 inch in diameter) had a shiny, continuous, tin core completely surrounded by polymer.

A sample of the filament was elongated 400% by draw' ing at room temperature (La, '5 times original length). This treatment fractured the core into small equal longitudinalysegments (of about .0035" in diameter and 0.017"

long and about 0.090" apart) so that the filament resembled that shown in FIGURE 11 with a diameter of about 0.0045 inch. Hand rolling of the drawnfilament with a metal roller flattened the'filament and afforded decorative ribbons 0.017 inch wide'and 0.002 inch thick, with a row of shiny, glittering, sequin-like segments of tin 0.012 inch wide, .0015 inch thick and 0.10 inch apart in the core oriented with the filament and completely surrounded by 'a polyester sheath with the appearance shown in FIG- URE 12. Physical properties of these products of this Example II are given below:

Ultimate Dry Elongation, Percent Tenacity 'Denier/ g.p.d. Fila- Treatment Mi 1 ment .As spun 0. Drawing 2. Drawing plus rollin 1 1 Initial'modulus of elastieity'ingrams per denier. 3

Reference to ultimate elongation herein, signifies the residual elongation in the filaments when stretched to the break under standard condiitons used for testing elongation.

Another sample of the same as-spun filament as above was hand-rolled with a metal roller to give an increase in length equivalent to a 70% elongation of the original The flattened filament with a continuous metal core had the cross-section of FIGURE 13.

The rolled filament was the'ndrawn over a pin at room temperature to give a total elongation of 250% of the The drawn filament had a continuous metal core and had the cross-section shown in FIGURE 14 where it can be noted that the filament cross-section partially reverted to round crosssection. Rolling of the drawn filament flattened the filament once more and gave a ribbon 0010" wide x 0.002" thick with a continuous sheath (uniform along its length) of polyester completely surrounding a continuous core oftin about 0.006" wide x 0.0008" thick throughout as shown in FIGURE 15. All these filaments displayed a bright shiny core but the reflectivity'was much greater with the rolled filaments in which the core was flattened during rolling. Physical properties of these products are given below: 7

v Ultimate Tenacity, Tensile Dry Denier} Filament Treatment g.p.d. Strength, Elonga- Ml Filap.s.i. -on, ment Percent Rolling plus drawing plus rolling l. 1 28, 500 70 21 260 All the filaments of this examplehaving continuous metal cores will conduct an electric current.

It was surprising that the above sequence of rolling and drawing allowed the tin core to be elongated to a total of 250% since the core of the as-spun filament fractured when elongated 23% by drawing without prior rolling. When it was attempted to roll and draw a length of, cast tin similar to the core 'of the above 'filament, the tin drew to a total elongation of about 30% before breaking after being increased in length 10% by rolling. The maximum tensile strength that could be obtained by drawing at room temperature short of fracturing the core was 9200 psi The improvement by first rolling is apparent.

Example III played a reflective, flattened continuous metal core completely surrounded by the polyamide sheath. The rolled and drawn filament had a tenacity of 0.76 g.p.d. (tensile strength of 42,800 p.s.i.), an ultimate elongation of 31%,

21 Mi of 12 g.p.d. and a denier, per filament of 391.

Example IV The polyamide in Example III was replaced with a 0 linear polyethylene having amelt index (ASTM Std Dl238-52T) of 4.7, a density of 0.96 and a melting point of C. and a filament melt-spun (using the equipment of Example II) by extruding the polyethylene at 250 C. simultaneously with the molten tin at 60 yards per minute into a water. quench as in Example II. Lengths of the filament containing a continuous tin core completely surrounded by a sheath of polyethylene could be elongated 60% by drawing after first elongating the filament 30% by.rolling.

The metal core of the filaments of this invention can be any metal that is molten at the spinning temperature of the molten polymer (the polymer may be melt-spun at any temperature at which it is not substantially decomposed). Preferably the metal has a melting point below the melting point of the polymer, particularly-in the case of polyamides and polyesters. Such metals include tin, lead, bismuth, selenium and their alloys with each other and with such metals as antimony and zinc, as, for example, bismuth solder, battery plate metal, white metal, aluminum solder, and the eutectic alloy of tin and lead. Higher melting alloys such as 70% aluminum 30% magnesium (melting point 435 C.), can

also be used.

For the sheath of the'filaments of this invention, any fiber-forming polymer that can be spun into filaments at a temperature at which the metal core is molten, can be used, such as polyesters, polyamides, ,polyethers polya I acetals, polyurethanes, polyureas, polyhydrocarbons as polyethylene and p olytetrafluoroethylene and polyvinyl polymers as polyacrylonitrile, polyvinyl chloride, poly vinylid ene chloride and their copolymers. Because of their commercial availability, ease of processing and excellent properties, polyesters, polyamides, or polyesteramides as described in US. Patents 2,071,250; 2,071,253; 2,130,523; 2,130,948; 2,190,770; 2,465,319and in other places are preferred. r r

- In the drawings, it is desired to point out that the small black specks occurring in the various views of filament cross-sections, e.g., FIGURES 10 and 13-16, represent having a fiat continuous metal core can be made by rollin'g'lor squeezing an as-spun filament made without any intentional drawing during and/or after spinning and so used, itfis generally preferable to further increase the strength of the filament through orientation by drawing, followed by a second rolling step. A part of the orientation obtained by a separate drawing step can, of course, be obtained instead by drawing during spinning, in which case the filaments are wound up at a rate much greater than that at which they are extruded from the spinneret.

The extent of such spin-draw possible will be limited by' the ultimate elongation of the metal under the temperature of the process.

Although this invention has been illustrated only with rolling and drawing steps as separate operations, it is obvious that such operations can be performed continuously in sequence. In addition, a filament can be efiecr tively rolled and drawn simultaneously by drawing it through a slit aifordedby the smooth edges of twopins of rolls that exert a constant pressure on the filament! 'Also', by drawing the metal-core filaments over a series of. pins arranged in a zigzag path so that the drawing tension applies a compressive force to the filament, a flattened filament with a continuous core can be obtained in a coritinuous process; it is a'dvantage'ous to perform such a {process at a temperature between '70 and 120 C.

' In spinning the filaments'of this invention, a relatively rapidi'rate of quenching is preferred in order to solidify the metal and so prevent possible formation of globules of metalin the core due tothe surface tension of the molten metal. Such quenching can be accomplished by extruding into a concurrent, countercurrent or cro'ss'flow of gas or by spinning into a liquid. i

I'he decorative filaments of this invention having intermittent platelets of metal; in the core can be made by drawing a compositefilament under such conditions that the :metal core fractures, and; thereafter rolling the filament. In general, this can be done at'temperatures below the melting point or minimum value'o'f the melting temperaturerange of a metaltwhere the metal does not have a .definiteinelting point), The total elongation of the'filament in the ,draw must exceed the ultimate elongation of the metal at the temperature of the draw. This will vary 7 from metal to metal, but in general, the elongation necessary, which-may range from 50m 1500% (to produce the desired strength in the polymeric sheath) will be sufficient to fracture the metal in the as-spun filaments. In order to provideenough strength for the polymer to hold its form during the drawing step, the sheath of the as-spunfilament should comprise about 5 to 95% of the filaments temperature, the core-to-sheath ratio can be adjusted to.

afford a segmented core by drawing.

;A given ratio of filament components is obtained with agiven spinneret by adjusting the flow rates of the two liquids that are spun, as, for example, by changing the polymer feed pump rate or by altering the gas pressure that might be used, for example, to extrude the molten metal. I

'With some metals having a sufficiently high surface tension, it is possible to obtain an intermittent core by drawing the filaments at temperatures above the melting point of the metal so that the metal contracts into segments in the core.

The appearance of the decorative filaments of this in-.

vention having intermittent platelets in the core can be varied between wide limits within the scope of't-his invention. I

The length of the metal segments before flatteningis considered to be a function of the sheath-to-core volume ratio, the tensile strengths of the two componentsand the compressive force .exertedby the sheath on the core. Thus, the length of the core segments in a given filament are increased by'using a stronger metal and/or a larger metal core, and decreased by using a weaker metal and/ or a smaller metal core.

Thegwidth of the platelets will be controlled by the The distance between the platelets n the final yarn can be varied from the smallest distance requiredifo r segmentation to 800% and larger of the filament diameter by varying, the total elongation after fracturing the core.

2 In general, a minimum distance. between platelets correreflective cores can be used to make all manner of novel sponding' to about 200% of the drawn filament diameter will be preferred in order for the filament to have high enough strength, and a maximum distance of about 400% of the drawn filament diameter will bepreferredin-order toretainthe decorative eifects of the filament. I

The filaments of this invention are of advantage in textile applications due to their, strength and appearance.

Those filaments with continuous or intermittent flattened fabrics The appearance of the filaments can be'altered by cospinning dyes or pigments in the polymer sheath or by dyeing the filaments or fabrics. In this way, filaments resembling gold lame can be formed, at a fraction of the cost of the conventional gold-wound or'gold-coated filaments. The opaqueness of the metal core to beta and gamma radiation can be utilized in the fabrieation'of volume; withthe range 25-to being preferred. The

total force to break the core must be less than the force requiredqto lbreak lthe sheath. Knowing the tensile strengths of the metal andthe polymer at the drawing clothing to provide protection against atom bomb debris, forexample. H ,1,

Those filaments with continuous metal cores can be used as insulated conductors, and those. having'very small diameter cores of low melting metals are useful as microampere fuses. Fabrics made of the filaments of this invention can be used to provide shielding around electronic equipment. The solubilities of the polymeric sheaths in various solvents can be used by applying a solvent for thepolymer to a cut fabric so as to bind the contacting .edges of the filaments in the fabric, for example, into a form-stable covering that will not be displaced, by vibration of the equipment and yet reduce the usual electronic noise; the same eflect may beobtaine d by fusing the edges of the fabric asby cutting'with a ,qknife heated to the melting point of the polymer.

Inasmuch as the filaments of this invention are especial- .ly useful-in textiles, it is preferred, that'filaments intended for this use have drawn denier of 2 to 2000 per filament. However, for other uses the denier per filament may be much larger, and is selected according to the useto which 7 the filaments areapplied.

Orientation of the filaments before rolling should be incomplete, i.e., the filaments should not be completely drawn prior to rolling. Preferably, the filaments should be undr-awn or drawn to a length not exceeding 90% of the length of the yarn (1.9x) if completely drawn at the rolling temperature. It is preferred that the rolling effect an elongation equal to at least 20% of the as-spun and undrawn length (whether or not drawing took place prior to rolling). Also, the total elongation of the yarn from all rolling and drawing steps (if drawing is used) should be at least 100%, i.e., the final filaments should have a length of at least two times the as-spun (undrawn) filaments; the term substantially oriented" when used in the claims, shall, unless indicated other wise, connote the said minimum elongation.

Any departure from the above description which con forms to the spirit of the invention is intended to be included within the scope of the claims.

I claim as my invention:

1. A substantially flat, composite filament comprising a substantially oriented sheath of synthetic linear polymer and a flat core of metal having a melting point below the decomposition point of the polymer.

2. A substantially flat, composite filament comprising a substantially oriented sheath of synthetic linear condensation polymer and a flat core of metal having a melting point below! the decomposition point of the polymer.

3. A substantially flat, composite filament comprising a substantially oriented sheath of synthetic linear polyamide and a flat core of metal having a melting point below that of the polyamide.

a substantially oriented sheath of synthetic linear polymer and a discontinuous core composed of metal platelets, of a metal having a melting point below that of the synthetic linear polymer.

References Cited in the file of this patent UNITED STATES PATENTS 2,174,9'12 Thielking Oct. 3, 1939 2,266,363 Graves Dec. 16, 194-1 2,308,638 Balthis et a1. Jan. 19, 1943 2,389,379 McCulloch Nov. 20, 1945 2,393,595 Dawson Jan. 29, 1946 2,554,663 Cowgill May 29, 1951 2,636,833 Borden Apr. 28, 1953 2,674,025 Ladisch Apr. 6, 1954 3,830,156 Burgess Apr. 8, 1958 FOREIGN PATENTS 278,387 Switzerland Ian. 16, 1952 907,876 Germany Mar. 29, 1954 710,084 Great Britain June 9, 1954 

1. A SUBSTANTIALLY FLAT, COMPOSITE FILAMENT COMPRISING A SUBSTANTIALLY ORIENTED SHEATH OF SYNTHETIC LINEAR POLYMER AND A FLAT CORE OF METAL HAVING A MELTING POINT BELOW THE DECOMPOSITION POINT OF THE POLYMER. 